Double patterning method

ABSTRACT

Self-aligned double patterning methods that can be used in back-end-of-line (BEOL) processing and other stages of integrate circuit device manufacturing. In these methods, line termini are masked prior to self-aligned double patterning. The self-aligned double patterning involves forming a mandrel, the shape of which is determined by a lithographic mask. That same lithographic mask is used prior to self-aligned double patterning to trim the mask that determines the locations of line termini. The methods provide precise positioning of the line termini mask relative to the line locations determined by self-aligned double patterning. The methods forms consistent end-of-line shapes and allow line termini to be placed more closely together than would otherwise be feasible.

REFERENCE TO RELATED APPLICATION

This application is a Non-Provisional application claiming priority toProvisional Patent Application Ser. No. 61/782,486 filed on Mar. 14,2013 in the name of Chia-Ying Lee, et al., entitled “DOUBLE PATTERNINGMETHOD” and is hereby incorporated by reference.

BACKGROUND

In conventional photolithography a photoresist is exposed to lightthrough a mask. The photoresist is modified by the exposure in such away that either the exposed or unexposed portions of the resist can beremoved during subsequent development. Any photolithographic process haslimitations, whereby there is a critical dimension below which featuresare too fine to be resolved. That resolution limit is a critical barrierin reducing the scale of integrated circuit devices.

Self-aligned double patterning is a technique for forming featureshaving a finer pitch than would be possible by the direct application ofa photolithographic process. Self-aligned double patterning involvesforming a mandrel having line-shaped features. A spacer formationprocess is then used to form spacers on the sides of the mandrelfeatures. The mandrel is then stripped leaving the spacers defining twosets of lines. A first set of lines corresponds to the mandrel. A secondset of lines is formed between each adjacent pair of the mandrel'sline-shaped features, the second set of lines being form betweenadjacent spacers.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flow chart of an integrated circuit manufacturing processthat is an embodiment of a process provided by the present disclosure.

FIG. 2 provides a partial plan view of an example integrated circuitdevice to which the process of FIG. 1 can be applied.

FIG. 3 is a cross section of the device illustrated by FIG. 2 takenalong the line A-A′.

FIGS. 4-25 are a series of paired plan and cross-sectional views showingprogression of the example integrated circuit device of FIGS. 2 and 3through processing by the method of FIG. 1.

FIG. 26 is a flow chart of an integrated circuit manufacturing processthat is an embodiment of another process provided by the presentdisclosure.

FIG. 27 provides a partial plan view of an example integrated circuitdevice to which the process of FIG. 26 can be applied.

FIG. 28 is a cross section of the device illustrated by FIG. 27 takenalong the line A-A′.

FIGS. 29-44 are a series of paired plan and cross-sectional viewsshowing progression of the example integrated circuit device of FIGS. 27and 28 through processing by the method of FIG. 26.

FIG. 45 is a flow chart of an integrated circuit manufacturing processthat is an embodiment of yet another process provided by the presentdisclosure.

FIG. 46 provides a partial plan view of an example integrated circuitdevice to which the process of FIG. 45 can be applied.

FIG. 47 is a cross section of the device illustrated by FIG. 46 takenalong the line B-B′.

FIG. 48 is a cross section of the device illustrated by FIG. 46 takenalong the line A-A′.

FIGS. 49-66 are a series of plan and cross-sectional views, each groupof three representing the device at a single stage, the collected viewsshowing progression of the example integrated circuit device of FIGS.46-48 through processing by the method of FIG. 45.

DETAILED DESCRIPTION

The line-shaped features produced by self-aligned double patterning havetermini. The masks that form these termini take the form of smallislands. These islands are ideally rectangular. In practice, theseislands become rounded. When these rounded mask shapes are slightlymisaligned with respect to the line-shaped features formed byself-aligned double patterning, the result can be acute corners that canlead to imperfect metal backfill. To avoid any backfill issues, theislands may be subjected to a supplemental trimming operation. Allowingfor this supplemental trimming places a minimum on the distance betweentermini. The minimum distance between termini is generally much largerthan the critical dimension for the photolithographic process.

The present disclosure relates to integrated circuit devicemanufacturing processes. The present disclosure provides self-aligneddouble patterning methods that can be used in back-end-of-line (BEOL)processing and other stages of integrated circuit device manufacturing.In these methods, line termini are masked prior to self-aligned doublepatterning. The self-aligned double patterning involves forming amandrel, the shape of which is determined by a lithographic mask. Thatsame lithographic mask is used prior to self-aligned double patterningto trim the mask that determines the locations of line termini. Themethods provide precise positioning of the line termini mask relative tothe line locations determined by self-aligned double patterning. Themethods allow line termini to be placed more closely together than wouldotherwise be feasible.

FIG. 1 provides a flow chart of an example process 100 of forming anexample integrated circuit device 200 according to an embodiment of thepresent disclosure. The process 100 begins with act 101, forming a firsthard mask layer (HM1) 203 on a substrate 201. The process 100 isconcerned with patterning HM1 203 for use in treating the substrate 201.In some embodiments, the substrate 201 comprises a semiconductor body.In some embodiments, the treatment applied using the method 100 formstrenches in the substrate 201. However, the method 100 and the otherexample methods provided by the present disclosure can be used to applyany treatment requiring a mask to a substrate of any type orcomposition. The process 100 patterns HM1 203. The pattern can be onethat has features finer than can be formed through photolithographywithout double patterning.

The process 100 continues with a group of acts 120 that form a secondhard mask layer (HM2) 205 over HM1 203. HM2 205 will be shaped byprocess 100 to define the positions at which line-shaped openings thatwill be formed into HM1 203 will terminate. In a following group of acts130, HM2 205 is trimmed. The trimming process 130 trims the features ofHM2 205 using a photolithography mask. That same mask will later be usedto define the shape of a mandrel for self-aligned double patterningprocess 140. Trimming narrows the line termini-defining features of HM2205 so as to trim these features in a way that determines the locationof their boundaries that are parallel to the terminated lines. Trimmingnarrows the termini-defining features and centers them with respect tothe terminated lines. This trimming and centering results in aconsistent shape for the line termini and reduces the possibility of anydefects that could be caused by irregularly shaped line termini.

The series of acts 120 begins with act 121, which is forming the layerHM2 205 over HM1 203. An example embodiment of the resulting structureis illustrated in FIGS. 2 and 3 by partially-formed integrated circuitdevice 200. FIG. 2 provides a plan view of the device 200. FIG. 3provides a cross-section of the device 200 taken along the line A-A′ ofFIG. 2.

The series of acts 120 continues with act 122, forming a photoresist(PR1) 207 and patterning PR1 207. The pattern determines the locations243 where lines 241 defined by subsequent self-aligned double patterning140 will terminate. These locations are identified in FIG. 6 and in FIG.24, which will be discussed in more detail subsequently. PR1 207 masksthe substrate 201 where the lines 241 will terminate. The structure ofPR1 207 following act 122 is illustrated in FIGS. 4 and 5.

Act 123 applies the pattern of PR1 207 to HM2 205 as illustrated byFIGS. 6 and 7. Act 122 is an etching operation in which PR1 207 operatesas a mask and HM1 203 operates as an etch stop layer. In someembodiments, HM1 203 is a single layer of material and the etchingconditions for act 123 are chosen to remove the materials of HM2 205 ata higher rate than the material of HM1 203. Following act 123, thepatterning of HM2 205 determines the locations 243 where lines 241 thatwill be formed by self-aligned double patterning 140 will terminate.Following act 123, PR1 can be stripped by act 124.

Act 123 patterns HM2 205 into islands 206, which are identified in FIG.6. The islands 206 will mask portions of the substrate 201 duringfurther process 161. Lines 241 will terminate at locations 243, whichbound the vertical extent of islands 206. The following series of acts130 reduces the horizontal extent of the islands 206. By reducing andaccurately determining the horizontal extent of the islands 206, lines241 can be terminated reliably, which in turn allows the end-to-endspacing 245 to be made smaller than would otherwise be feasible.

The series of acts 130 that trim HM2 205 begin with act 131, which isforming a photoresist (PR2) 209 and patterning PR2 209 using aphotolithographic mask PM1 (not shown in the figures). PM1 is used againin act 143 to pattern a photoresist (PR3 215), that will shape themandrel for self-aligned double patterning 140. Act 131 shapes PR2 209into lines of width 210, as illustrated by FIGS. 8 and 9.

Act 132 is an etching operation that trims HM2 205 where it is notmasked by PR2 209. Act 132 trims HM2 205 as illustrated by FIGS. 10 and11. Act 132 is an etching operation in which PR2 209 operates as a maskand HM1 203 operates as an etch stop layer. In some embodiments, HM1 203is a single layer of material and the etching conditions for act 132 arechosen to remove the materials of HM2 205 at a higher rate than thematerial of HM1 203. Following act 132, PR2 can be stripped by act 133.

In some alternative embodiments, the acts 120 that form the line terminimask and the acts 130 that trim the line termini mask are combined touse one photoresist. For example, after PR1 is exposed through the linetermini mask in act 122, PR1 can be exposed again through the mandrelmask in a counterpart to act 131. HM2 203 can then be patterned in oneaction that combines acts 123 and 132.

Following acts 130, which complete the patterning of HM2 205, theprocess 100 proceeds with self-aligned double patterning 140.Self-aligned double patterning 140 begins with act 141, which formssacrificial hard mask layer (SHM1) 211. SHM1 211 overlies HM1 203 andHM2 205 and provides a planar surface on which a mandrel and spacers canbe formed. In some embodiments, SHM1 211 is eliminated and HM1 203 andHM1 205 provide the etch stop functionality otherwise provided by SHM1211. Eliminating act 141 and SHM1 211 simplifies the process 100. Inmost embodiments, however, SHM1 211 is included to avoid thepossibilities of spacers forming along sidewalls of HM2 205.

SHM1 211 can contain multiple layers of disparate materials. In theembodiment 200 illustrated by FIGS. 12 and 13, SHM1 211 includes twolayer, layers 217 and 218. In some embodiments, the upper layer 218provides the functionality of an etch stop layer. In some embodiments,the upper layer 218 provides the functionality of an antireflectivecoating. In some embodiments, the upper layer 218 provides both of thesefunctionalities. The composition of SHM1 211 and the number of layers itcontains can be selected to provide the etch selectivity required duringsubsequent processing.

Act 142 forms sacrificial hard mask layer (SHM2) 213, which is the layerthat is patterned to form the mandrel. As illustrated by FIGS. 12 and13, for the example device 200 SHM2 213 includes two layers, layers 219and 220. In some embodiments, the upper layer 220 provides anantireflective coating. The composition of SHM2 213 and the number oflayers it contains can be selected to provide the etch selectivityrequired during subsequent processing.

Act 143 forms and patterns a photoresist (PR3) 215 over SHM1 211 andSHM2 213. PR3 215 is patterned to the form of a mandrel as shown inFIGS. 12 and 13. PR3 215 is patterned using the photolithographic maskPM1, which is the same mask previously used to pattern PR2 209 in act122 for trimming HM2 in act 123. Photolithography shapes PR3 209 intolines of width 212.

As can be seen in FIG. 12, the width 212 is smaller than the width 210even though these line widths result from application of the samephotolithographic mask PM1. The difference in widths is desirable toensure that the islands 206 of HM2 205 are sufficiently broad to servetheir function of terminating lines. In some embodiments, the differencebetween the width 210 and the width 212 is equal to at least twice theuncertainty in the alignment of photolithographic mask PM1 with respectto the device 200. In some embodiments, the width 210 is greater thanthe width 212 by an amount equal to from about 10% to about 180% thewidth of spacer 221, which are formed by act 146. In some embodiments,the width 210 is from 3 nm to 30 nm greater than the width 212. Thedifference in width can be achieved by varying the conditions ofexposure, varying the chemistry of the photoresists PR2 209 and PR3 215,or a combination of the two. In some embodiments, PR2 209 is a positivephotoresist and is under exposed in act 131. In some embodiments, PR3215 is a positive photoresist and is over exposed in act 145. In someembodiments, PR2 209 is exposed for a longer period than PR3 215.

Act 144 applies the pattern of PR3 215 to SHM2 213 thereby forming SHM2213 into a mandrel as illustrated by FIGS. 14 and 15. Act 144 is anetching operation with PR3 215 providing the mask and the upper surfaceof SHM1 211 (layer 218) providing an etch stop. Any suitable etchprocess can be used. In one example, act 144 includes an initialbreakthrough etch to penetrate the layer 220 followed by a main etch.While in most embodiments, the main etch has a high selectivity forremoving the material of layer 219 over the material of layer 218, thebreakthrough etch does not require this selectivity and can have theopposite selectivity. Following act 144, PR3 215 can be stripped by act145.

Act 143 forms PR3 219 to the shape of the mandrel. As can be seen bycomparing FIGS. 12-13 and FIGS. 14-15, acts 144 and 145 transfer themandrel shape of PR3 219 to SHM2 213. In some examples, a photoresistmaterial is suited to the function of SHM2 213 and can serve as themandrel. Accordingly, in some embodiments, PR3 219 is used in place ofSHM2 213 and acts 142, 144, and 145 are eliminated.

Act 146 forms spacers 221 adjacent the features of SHM2 213 (themandrel) to produce a structure as illustrated in FIGS. 16 and 17. Inother words, act 146 forms spacers to the sides of SHM2 213. Act 146 caninclude depositing a spacer material, then etching anisotropically toform spacers 221. Spacers 221 can be formed from any suitable material.Examples of materials that can be suitable include SiO, SiN, TiO, TiN,Ta, and TaN. The material can be deposited by any suitable method, forexample ALD or CVD. Etching conditions can be typical for spacerformation.

Act 147 removes the mandrel SHM2 213. Act 148 etches SHM1 except wheremasked by spacers 221. These two acts can be combined into a single etchprocess. In either case, the result is a structure as illustrated byFIGS. 18 and 19. Act 148, or the combined acts 147 and 148, are etchoperations with spacers 221 providing a mask and HM2 205 providing anetch stop layer. HM1 203 can also be used as an etch stop layer, butthis is not necessary in that the act 148, which follows, continuesetching through HM1 203. Spacers 211 do not mask any part of SHM2 213,therefore SHM2 213 is removed entirely by act 147 regardless of whetheracts 147 and 148 are combined. The etch can use conditions that vary tosequentially etch through the layers 220, 219, 218, and 217 whileproviding a desired etch rate and etch selectivity.

Act 149 etches HM1 203 except where HM1 203 is masked by either HM2 205or spacers 221. FIGS. 20 and 21 provide an example of the resultingstructure. Act 149 is an etch operation having conditions thatselectively remove the material of HM1 203 over the material of HM2 205.The compositions of HM1 203 and HM2 205 can be selected to facilitatethis operation.

Act 150 removes spacers 221 and the remaining portion of SHM1 211. FIGS.22 and 23 provide an example of the resulting structure. Act 150 canalso remove HM2 205. Portions of the substrate 201 that are masked byHM2 205 are also masked by HM1 203, therefore HM2 205 is no longerrequired.

Self-aligned double patterning 140 patterns HM1 203 into a mask definingtwo sets of lines as illustrated in FIGS. 22 and 23. Lines 241 are inlocations previously masked by the mandrel SHM2 213. Lines 241 areinterleaved with lines 242. Lines 242 are formed between locations thatwere masked by spacers 221. Lines 241 have termini 243 identified inFIG. 22. The locations of termini 243 are determined by the patterningof HM2 205. The precise patterning of HM2 205 through acts 120 and 130permits the distance 245 between termini 243 to be smaller than wouldotherwise be feasible.

The series of act 160 are one or more acts in which the substrate 201 isprocessed using the patterned mask HM1 203. The processing can be anyprocessing that is facilitated by HM1 203. Examples of processes thatcan be facilitated by patterned mask HM1 203 include etching and ionimplantation. Act 161 is illustrative of the type of processing that ispossible. Act 161 forms trenches in the substrate 201 as illustrated byFIGS. 24 and 25. Act 161 is an etch for which HM1 203 provides a mask.In some embodiments, the trenches are formed in a dielectric layer ofsubstrate 201. In some embodiments, the dielectric is a low-kdielectric. In some embodiments, the trenches are formed as part of adamascene or dual damascene process that forms a metal interconnectstructure for the device 200.

The process 100 provides an example of embodiments in which line termini243 are formed for lines 241. FIG. 26 provides a flowchart of process250, which is an example of embodiments in which line termini 243 areformed for lines 242. The components of process 250 are similar to thoseof process 100. The description of process 250 generally applies toprocess 100.

The principle difference is in the manner of patterning PR2 209 usingthe photolithographic mask PM1 for the purpose of trimming HM2 205. Inact 131 of process 100, PR2 209 is a resist of the same type (positiveor negative) as PR3 215. Process 250 substitutes act 251, which is thesame as act 131 accept that PR2 301 is used instead. PR2 301 is aphotoresist of the opposite type from PR3 215. Whereas act 131 producesa structure such as the one illustrated by FIGS. 8 and 9, act 251produces a structure such as the one illustrated by FIGS. 27 and 28.Whereas act 131 shapes PR2 209 into lines of width 210, as illustratedby FIGS. 8 and 9, act 251 shapes PR2 310 in a mask with line-shaped gapshaving width 210 as illustrated by FIGS. 27 and 28. PR2 310 is patternedto the inverse of PR2 209.

FIGS. 29-44 show how this change affects the device 200 throughsubsequent processing. In process 250, trimming 130 patterns HM2 205 tothe form illustrated in FIGS. 29 and 30. In this form, HM2 205 includesislands 306 that will form termini for lines 242. Additional islands 308may also remain. Additional islands 308 are located over areas of thesubstrate 201 that will be masked by spacers 221. Therefore, islands 308have no significant effect on the final form of device 200.

As shown in FIGS. 31-34, when SHM2 213 is formed and patterned into themandrel SHM2 213, islands 306 and 308 flank mandrel features. Afterspacers 221 are formed and the mandrel SHM2 213 is removed as shown inFIGS. 35-38, the islands 306 and 308 flank the gaps 310 as shown in FIG.38. As illustrated by FIGS. 39-44, the gaps 310 are the locations wherelines 241 will be formed. Selecting the conditions for act 251 vis-à-visthe conditions for act 144 to make the width 210 greater than the width212 allows for some difference in the alignment of photolithographicmask PM1 between its use in act 251 and its use again in act 144 withouteither of the islands 306 and 308 intruding into the gaps 310.Differences in width can be achieved by under or over exposure of thephotoresist PR2 209 in act 251 or PR3 219 in act 141. Under exposure ofa negative photoresist can be substituted for over exposure of apositive photoresist and vice versa. As for embodiments of process 100,in some embodiments of process 250 the difference between the width 210and the width 212 is from about 3 nm to about 30 nm.

The process 100 provides an example of embodiments in which line termini243 are formed for lines 241. The process 250 provides an example ofembodiments in which line termini 243 are formed for lines 242. FIG. 45provides a flowchart of process 350, which is an example of embodimentsin which line termini 243 are formed for both lines 241 and lines 242.

The components of process 350 are similar to those of process 250.Process 350 includes act 251, which forms the inverse-patterned PR2 301for trimming the line termini-defining HM2 205. The description ofprocess 250 generally applies to process 350. The principle differenceis the addition of acts 351 to 353 to self-aligned double patterning140. Acts 351 to 353 form gaps 406 in the mandrel SHM2 213 as shown inFIGS. 52-54. In process 350, spacer formation 146 fills gaps 406 withblocks 404 of spacer material 221 as shown in FIGS. 55-57. The block 404of spacer material 221 form termini 243 for lines 241 as shown in FIGS.58-66.

Act 351 forms and patterns a photoresist (PR4) 401. Patterning formswindows 402 in photoresist 401 as illustrated by FIGS. 46-48. Windows402 expose the mandrel SHM2 213 at location were gaps 406 are desired.Act 352 is an etching operation for which PR4 401 provides a mask andSHM1 211 providing an etch stop. In terms of the layers removed, this issimilar to act 144, which applies the mandrel pattern to SHM2 213.However, whereas in act 144 SHM1 211 is only exposed during the latterstaged of the etching procedure, in act 352 a portion of SHM1 211 isexposed throughout the etching process. Accordingly, the selection ofsuitable materials for process 350 is more demanding as compared process250.

In some alternative embodiments to process 350, the mandrel SHM2 213 isformed with gaps 406, which eliminates the need for PR4 401. As oneexample, following exposure of PR3 215 though the photolithographic maskPM1 in act 144, PR3 215 is again exposed through the gap-defining maskof act 351. Developing the PR3 215 and using it to pattern SHM2 213 inact 144 then forms SHM2 213 to the mandrel with gaps as shown ion FIGS.52-54.

In one example of process 350, the base material etched in act 161 is alow k dielectric. HM1 203 is either a Ti, Ta, or a compound of Ti or Ta.HM2 205 is a silicon compound such as SiO, SiC, or SiN. SHM1 211 eachinclude a carbon-based lower layer and a silicon-containing upper layer.

In some embodiments the substrate 201 includes a semiconductor body andone or more device structures formed during front-end of line (FEOL)processing. Examples of semiconductors include, without limitation,silicon, silicon on insulator (SOD, Ge, SiC, GaAs, GaAlAs, InP, GaNSiGe. Device structures formed during FEOL processing can include,without limitation, memory devices, logical devices, FETs and componentsthereof such as source regions, drain regions, and gate electrodes,active devices, passive devices, and combinations thereof. The substrate201 can also include insulators, conductors, and previously formedinterconnect structures, including structures formed during back-end ofline (BEOL) processing. An upper layer of the substrate 201 can be adielectric or a sacrificial layer in which a metal interconnectstructure is to be formed.

In some embodiments, act 161 forms trenches in a layer of low-kdielectric. A low-k dielectric is one having a lower dielectric constantthan silicon dioxide. Examples of low-k dielectrics includeorganosilicate glasses (OSG) such as carbon-doped silicon dioxide,fluorine-doped silicon dioxide (otherwise referred to as fluorinatedsilica glass (or FSG), and organic polymer low-k dielectrics. Examplesof organic polymer low-k dielectrics include polyarylene ether,polyimide (PI), benzocyclobutene, and amorphous polytetrafluoroethylene(PTFE).

HM1 203 can be formed from one or more layers of any suitable materialor combination of materials. A suitable HM1 203 can have a compositionadapted to the requirements of further processing 160. A suitable HM1203 can be functional as an etch stop layer for etching HM2 205. Asuitable HM1 203 can be etched while HM2 205 and spacers 221 operate asmasks. In some embodiments, HM1 203 includes at least one layer of amaterial selected from the group consisting of Ti, TiN, Ta, and TaN. HM1203 can be deposited by any suitable method. Examples of methods thatcan be suitable include, without limitation, physical vapor deposition(PVD), chemical vapor deposition (CVD), and atomic layer deposition(ALD).

HM1 205 can be formed from one or more layers of any suitable materialor combination of materials. A suitable HM2 205 can be functional as amask for etching HM1 203. In some embodiments, HM1 203 includes at leastone layer of a material selected from the group consisting of SiO, SiC,and SiN. HM2 205 can be deposited by any suitable method. Examples ofmethods that can be suitable include, without limitation, plasmaenhanced chemical vapor deposition (PECVD), chemical vapor deposition(CVD), and atomic layer deposition (ALD).

SHM1 211 can be formed from one or more layers of any suitable materialor combination of materials. A suitable SHM1 211 can be functional toprovide a planar surface on which to form spacers 211 and to form andpattern SHM2 213 (the mandrel). In some embodiments, SHM1 211 includesat least an upper layer of a material selected from the group consistingof a Si-containing anti-reflective coating (BARC) material such as SiONor SiN. In some embodiments, SHM1 211 includes at least a lower layer ofa material of a carbon-based material selected from the group consistingof spin-on carbon, photoresist, and advanced patterning film (APF). Thelayers of SHM1 211 can be deposited by any suitable method. Examples ofmethods that can be suitable include, without limitation, spin coating,plasma enhanced chemical vapor deposition (PECVD), chemical vapordeposition (CVD), and atomic layer deposition (ALD).

SHM2 213 can be formed from one or more layers of any suitable materialor combination of materials. A suitable SHM2 213 can be functional toprovide a mandrel for forming spacers 211. In some embodiments, SHM2 213is a photoresist. In some embodiments, SHM2 213 includes at least anupper layer of a material selected from the group consisting of aSi-containing anti-reflective coating (BARC) material such as SiON orSiN. In some embodiments, SHM2 213 includes at least a lower layer of amaterial of a carbon-based material selected from the group consistingof spin-on carbon, photoresist, and advanced patterning film (APF). Thelayers of SHM2 213 can be deposited by any suitable method. Examples ofmethods that can be suitable include, without limitation, spin coating,plasma enhanced chemical vapor deposition (PECVD), chemical vapordeposition (CVD), and atomic layer deposition (ALD).

The photoresists PR1 207, PR2 209, PR3 215, PR3 301, and PR4 401 can beformed by any suitable processes and from any suitable materials. Atypical process is spin coating. Spin coating has the advantage ofproviding the photoresist with a comparatively uniform surface even whenthe underlying surface is comparatively irregular. The photoresists canbe positive or negative and can be patterned by any suitable process.Patterning can involve selective exposure to light, the selectivitybeing defined by photolithographic masks through which the light passes.Exposure modifies the photoresist in such a way that in subsequentdevelopment either only the exposed portions are removed, which is thecase for a positive resist, or only the unexposed portions are removed,which is the case for a negative photoresist. Photoresists can bestripped by any suitable processes. A positive photoresist can bestripped, for example, by non-selective exposure followed by developing.

The present disclosure refers to horizontal and vertical directions. Themeaning of these terms is self-evident in the figures. More generally,the vertical direction is the direction of run for a group of lines 241and 242 generated by self-aligned double patterning 140. The verticaldirection may vary over disparate areas of the substrate 201, butlocally there is only one direction to which this description applies.The horizontal direction is perpendicular to the vertical direction.

Lines 241 are portions of line-shaped features of the mandrel SHM2 213.Line-shaped features are elongated structures. They need not bestraight, but any curvature is generally gradual. A large degree ofcurvature may be evident in an overview of a line-shaped feature, butwhen focusing on a small portion or area of a line shaped feature, ingeneral, little or no curvature is evident.

The present disclosure describes a process of forming an integratedcircuit device. The process includes forming first and second hard masklayers over a substrate. The second mask layer is patterned by a processthat includes exposing a first photoresist through a first lithographicmask. A sacrificial layer is formed and patterned to form a mandrelabove the patterned second mask layer. Patterning the mandrel includesexposing a second photoresist through the first lithographic mask. Aspacer material is deposited over the mandrel and etched to form spacerson the sides of the mandrel. The mandrel is removed. The first hard masklayer is etched with the remaining second hard mask layer and thespacers providing a mask. The substrate is treated with the remainingfirst hard mask layer providing a mask.

The present disclosure also describes a method of forming an integratedcircuit device. The method includes forming a first hard mask layer overa substrate and forming a second hard mask layer over the first hardmask layer. A first photoresist layer is formed above the first andsecond hard mask layers. The first photoresist is exposed through amandrel mask. The first photoresist is developed to form a firstphotoresist mask. The second hard mask layer is patterned using thefirst photoresist as a mask and the first hard mask layer as an etchstop layer. Patterning the second hard mask layer forms a second layermask that defines locations at which conductive lines that will beformed in the substrate will end. The first hard mask layer is thensubjected to self-aligned double pattering to form a first layer mask.The first layer mask defines locations at which conductive lines will beformed in the substrate. The first layer remains intact where it ismasked by the second layer. The mandrel mask is used to form a mandrelfor the self-aligned double patterning. Trenches are formed in thesubstrate by etching with first layer mask providing a mask, andoptionally the second layer mask also providing a mask. The trenches arefilled with conductive metal.

The present disclosure provides a method of forming an integratedcircuit device. The method includes forming a first hard mask layer overa substrate and forming a second hard mask layer over the first hardmask layer. The second hard mask layer is patterned to form islands. Thefirst hard mask layer is then pattern be self-aligned double-patterning.In this method, self-aligned double-patterning includes forming amandrel using a mandrel mask and the second hard mask layer is trimmedusing this same mask. Self-aligned double patterning forms line-shapedopenings in the first hard mask. The islands mask termini of theline-shaped openings.

The components and features of the present disclosure have been shownand/or described in terms of certain embodiments and examples. While aparticular component or feature, or a broad or narrow formulation ofthat component or feature, may have been described in relation to onlyone embodiment or one example, all components and features in eithertheir broad or narrow formulations may be combined with other componentsor features to the extent such combinations would be recognized aslogical by one of ordinary skill in the art.

The invention claimed is:
 1. A method of forming an integrated circuitdevice, comprising: forming a first hard mask layer over a substrate;forming a second hard mask layer over the first hard mask layer; forminga first photoresist layer over the first and second hard mask layers;exposing the first photoresist layer through a mandrel mask; developingthe first photoresist layer to form a mask; patterning the second hardmask layer to form a second layer mask that defines locations at whichconductive lines that will be formed in the substrate will end, whereinpatterning comprises etching the second hard mask layer using the firstphotoresist layer as a mask and the first hard mask layer as an etchstop layer; performing a self-aligned double-patterning of the firsthard mask layer to form a first layer mask, wherein the first layer maskdefines the locations at which the conductive lines will be formed inthe substrate, wherein the first layer mask remains intact where it ismasked by the second layer mask, and wherein performing the self-aligneddouble-patterning comprises forming a mandrel over the patterned secondhard mask layer using the mandrel mask and subsequently etching thefirst hard mask layer; forming trenches in the substrate by etching withthe first layer mask providing a mask; and filling the trenches withconductive metal to form the conductive lines.
 2. The method of claim 1,wherein: there is a first ratio between the width of openings in themandrel mask and the width of corresponding areas of the firstphotoresist layer that are affected by exposure through the mandrelmask; there is a second ratio between the width of the openings in themandrel mask and the width of corresponding features of the mandrel; andthe first ratio is significantly greater than the second ratio.
 3. Themethod of claim 1, wherein: the widths of areas of the first photoresistlayer that are affected by exposure through the mandrel mask is greaterthan the widths of corresponding features of the mandrel; and thedifferences in the widths are greater than or equal to the uncertaintyin alignment between the mandrel mask and the substrate.
 4. The methodof claim 1, wherein the first photoresist layer is a negativephotoresist.
 5. The method of claim 1, wherein the self-aligneddouble-patterning is performed after patterning the second hard masklayer, and wherein the self-aligned double-patterning comprises: formingthe mandrel; forming spacers on sides of the mandrel; and stripping themandrel.
 6. The method of claim 5, further comprising: prior to formingthe spacers, forming narrow gaps in the mandrel; wherein the spacersform in the gaps and span the gaps.
 7. The method of claim 1, whereinthe second hard mask layer is patterned to define the locations at whichthe conductive lines will end and subsequently trimmed using the maskformed from the first photoresist layer.
 8. The method of claim 1,wherein: the widths of some of the trenches correspond to the widths offeatures in the mandrel; the widths of some others of the trenchescorrespond to the distances between adjacent spacers; and the secondhard mask layer determines the endpoints of some of the trenches.
 9. Amethod of forming an integrated circuit device, comprising: forming afirst hard mask layer over a substrate; forming a second hard mask layerover the first hard mask layer; patterning the second hard mask layer toform islands, wherein patterning the second hard mask layer comprisesinitially etching the second hard mask layer according to a termini maskand subsequently etching the second hard mask layer according a mandrelmask to trim the second hard mask layer; and performing a self-aligneddouble-patterning of the first hard mask layer using the patternedsecond hard mask layer, wherein the self-aligned double-patterningcomprises forming a mandrel over the patterned second hard mask layerusing the mandrel mask and forming line-shaped openings in the firsthard mask layer, and wherein the islands mask termini of the line-shapedopenings.
 10. The method of claim 1, wherein performing the self-aligneddouble-patterning of the first hard mask layer, comprises: forming asacrificial hard mask layer over the first mask hard layer and thepatterned second hard mask layer; patterning a second photoresist layeroverlying the second hard mask layer to form the mandrel; formingspacers on sides of the mandrel; removing the mandrel; and etchingthrough the first hard mask layer with the remaining second hard masklayer and the spacers.
 11. The method of claim 1, wherein the trenchesextend into a dielectric layer of the substrate.
 12. A method of formingan integrated circuit device, comprising: forming a first hard masklayer over a substrate; forming a second hard mask layer over the firsthard mask layer; forming a photoresist layer over the first and secondhard mask layers; exposing the photoresist layer through a mandrel mask;developing the photoresist layer to form a mask, the mask comprising aline-shaped feature with a first width; patterning the second hard masklayer to form a second layer mask that defines locations at whichconductive lines that will be formed in the substrate will end, whereinpatterning the second hard mask layer comprises etching the second hardmask layer using the photoresist layer as a mask and the first hard masklayer as an etch stop layer; after patterning the second hard masklayer, performing a self-aligned double-patterning of the first hardmask layer to form a first layer mask, wherein the first layer maskdefines the locations at which the conductive lines will be formed inthe substrate, wherein the first hard mask layer remains intact where itis masked by the second layer mask, and wherein performing theself-aligned double-patterning comprises forming a mandrel over thesecond mask layer using the mandrel mask and subsequently etching thefirst hard mask layer, wherein the mandrel has a second width differentthan the first width; forming trenches in the substrate by etching withthe first layer mask providing a mask; and filling the trenches withconductive metal to form the conductive lines.
 13. The method accordingto claim 12, wherein the substrate comprises a semiconductor body and anoverlying dielectric layer, and wherein the trenches are formed over thesemiconductor body in the dielectric layer.
 14. The method according toclaim 12, wherein performing the self-aligned double patterning furthercomprises: forming a sacrificial hard mask layer over the first hardmask layer and the patterned second hard mask layer; patterning thesacrificial hard mask layer to form the mandrel by processes thatinclude exposing a second photoresist layer through the mandrel mask;forming spacers on sides of the mandrel; removing the mandrel; andetching through the first hard mask layer with the remaining second hardmask layer and the spacers as masks.
 15. The method of claim 14, whereinforming spacers on sides of the mandrel comprises: depositing a spacermaterial over the mandrel; and etching the spacer material to formspacers on the sides of the mandrel.
 16. The method of claim 15, furthercomprising: prior to depositing the spacer material, performing anadditional masked etch to form gaps in the mandrel; and wherein the gapsare sufficiently narrow that etching the spacer material to form spacersleaves the spacer material spanning the gaps.
 17. The method of claim12, further comprising: before forming the photoresist layer, initiallypatterning the second hard mask layer using a termini mask independentof the mandrel mask.
 18. The method of claim 17, wherein initiallypatterning the second hard mask layer comprises: forming a secondphotoresist layer over the second hard mask layer; selectively exposingthe second photoresist layer through the termini mask; developing thesecond photoresist layer; etching the second hard mask layer with thesecond photoresist layer providing a mask, wherein the etching does notpenetrate the first hard mask layer; and stripping the secondphotoresist layer.
 19. The method of claim 18, wherein the photoresistlayer is of opposite type from the second photoresist layer.
 20. Themethod of claim 12, wherein the mandrel has lined shaped-features,wherein etching forms the trenches in the substrate between locations ofthe line shaped-features, and wherein the second hard mask layerdetermines termini of the trenches.